/*
* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/

#ifndef B2_MOUSE_JOINT_H
#define B2_MOUSE_JOINT_H

#include <Box2D/Dynamics/Joints/b2Joint.h>

/// Mouse joint definition. This requires a world target point,
/// tuning parameters, and the time step.
struct b2MouseJointDef : public b2JointDef
{
    b2MouseJointDef()
    {
        type = e_mouseJoint;
        target.Set(0.0f, 0.0f);
        maxForce = 0.0f;
        frequencyHz = 5.0f;
        dampingRatio = 0.7f;
    }

    /// The initial world target point. This is assumed
    /// to coincide with the body anchor initially.
    b2Vec2 target;

    /// The maximum constraint force that can be exerted
    /// to move the candidate body. Usually you will express
    /// as some multiple of the weight (multiplier * mass * gravity).
    float32 maxForce;

    /// The response speed.
    float32 frequencyHz;

    /// The damping ratio. 0 = no damping, 1 = critical damping.
    float32 dampingRatio;
};

/// A mouse joint is used to make a point on a body track a
/// specified world point. This a soft constraint with a maximum
/// force. This allows the constraint to stretch and without
/// applying huge forces.
/// NOTE: this joint is not documented in the manual because it was
/// developed to be used in the testbed. If you want to learn how to
/// use the mouse joint, look at the testbed.
class b2MouseJoint : public b2Joint
{
public:

    /// Implements b2Joint.
    b2Vec2 GetAnchorA() const;

    /// Implements b2Joint.
    b2Vec2 GetAnchorB() const;

    /// Implements b2Joint.
    b2Vec2 GetReactionForce(float32 inv_dt) const;

    /// Implements b2Joint.
    float32 GetReactionTorque(float32 inv_dt) const;

    /// Use this to update the target point.
    void SetTarget(const b2Vec2& target);
    const b2Vec2& GetTarget() const;

    /// Set/get the maximum force in Newtons.
    void SetMaxForce(float32 force);
    float32 GetMaxForce() const;

    /// Set/get the frequency in Hertz.
    void SetFrequency(float32 hz);
    float32 GetFrequency() const;

    /// Set/get the damping ratio (dimensionless).
    void SetDampingRatio(float32 ratio);
    float32 GetDampingRatio() const;

    /// The mouse joint does not support dumping.
    void Dump() { b2Log("Mouse joint dumping is not supported.\n"); }

protected:
    friend class b2Joint;

    b2MouseJoint(const b2MouseJointDef* def);

    void InitVelocityConstraints(const b2SolverData& data);
    void SolveVelocityConstraints(const b2SolverData& data);
    bool SolvePositionConstraints(const b2SolverData& data);

    b2Vec2 m_localAnchorB;
    b2Vec2 m_targetA;
    float32 m_frequencyHz;
    float32 m_dampingRatio;
    float32 m_beta;
    
    // Solver shared
    b2Vec2 m_impulse;
    float32 m_maxForce;
    float32 m_gamma;

    // Solver temp
    int32 m_indexA;
    int32 m_indexB;
    b2Vec2 m_rB;
    b2Vec2 m_localCenterB;
    float32 m_invMassB;
    float32 m_invIB;
    b2Mat22 m_mass;
    b2Vec2 m_C;
};

#endif
